Patent GB-858837-A (GB)
Title: Improvements relating to automatic telephone exchange systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/42
Filed: 1958-09-22
Abstract: 858,837. Automatic exchange systems. SIEMENS EDISON SWAN Ltd. Sept. 11, 1959 [Sept. 22, 1958], No. 30222/58. Class 40 (4). In an exchange in which the selectors are controlled from a register by revertive impulsing the register comprises a number of stores, one for each digit, which record the complements of the dialled digits and are set in succession by counting out a temporary store which records each digit as it is dialled. The arrangement is advantageous for inter-exchange working where certain of the recorded digits require to be transmitted over an outgoing junction. As shown, all the stores as well as a distributer associated with them comprise multi-cathode discharge tubes. The selectors are of the motordriven uniselector type provided with wiperswitching, that at the final selector being dependent on " digit-pairing " at the first selector. The various gates and 2-state circuits are preferably constituted by transistors. Setting of register.-The calling line is connected over wire 11 to a circuit ABC which performs the functions of the A, B and C relays. A first selector X is seized over wires RL1... RL3, and relays TC, TA are energized. The tubes comprising the temporary digit store TDS, the digit complement stores DS1 ... DS4 and the distributer D are set to their starting positions. The store TDS is stepped by dialled impulses over wire 12, and at the end of the first train a two-state circuit TTD responds to a pulse on wire l4 to start a generator IG1 which sends impulses to the first digit complement store DS1 via gate GD1 and to the store TDS until the latter again reaches 0. At this point a pulse on wire l6 restores the circuit TTD and steps the distributer D to position 2 to open gate GD2 leading to the second digit complement store DS2. This and subsequent digits are thus recorded in a similar manner. Control of selectors.-With the distributer D in position 5 gates GW1 . . . GW3 are opened to permit the operation over terminals marked by DS1, DS2 of relays WSA, WSB, WP if required to control wiper-switching. Relays WT, WA energize temporarily to effect this operation in the first selector, TA releases and D advances to position 6. The first selector now steps and sends back alternate positive and negative impulses for each group of outlets, these passing via a bounce-eliminating circuit BE to advance DS1 until it reaches end-of-count condition 1, when a 2-state circuit TT1 operates over terminal eca, and gate GT1 is opened to connect test relay TA to the P-wiper. If no idle outlet is found in the group, the next revertive impulse resets TT1 and the selector continues to a penultimate position. If an idle outlet is found, TA reoperates, and stops the selector. Relays WT, WA again energize temporarily, resetting TT1 and starting the control of the second selector, including wiper-switching, if necessary. In the case of the final selector, revertive impulses sent from each outlet advance DS4, and DS3 is stepped each time DS4 reaches position 0. With DS3 in position 1 and DS4 in 0, gate GF opens so that the next impulse operates a 2-state circuit TT3 to permit testing of the wanted outlet. Inter-exchange working.-When an outgoing junction is seized by the first or second selector, relay J energizes over the + wire, makes an impulsing loop and alters the circuits controlled by the distributer D. A generator IG2 sends impulses to step the last-used digit complement store to position 7, whereupon a 2-state circuit TTJ operates over terminal ip to open gate 1HG2 and allow impulses to be repeated over the junction by relay PU. At the same time D advances one step and impulses step the next digit complementary store. When this reaches 0, TTJ is reset to end the repeated digit, and the store is stepped on to position 7 to measure the inter-train pause. The remainder of the digits are sent over the junction in a similar manner.